Ensure that your refrigerator is plugged in. Open the door of the fridge and look inside. If there is power to the fridge, but the fridge isn't cool, then there likely is a problem with the compressor and/or fan.
Listen to the rear of the refrigerator. If you hear a loud humming noise emanating from the bottom of the back of the fridge this could mean the fan is faulty.
Unplug the refrigerator and remove the screws from the rear panel of the unit with your Phillips screwdriver.
Remove the rear panel of the unit. You will see the compressor assembly. The fan will be attached to it.
Plug the refrigerator back in. If the blades of the fan don't spin then the fan is bad and needs to be replaced. This should be done by a professional.